The threat posed by small ballistic weapons such as rocket-propelled grenades (RPGs) and shoulder fired missiles is significant and well documented. Attacks are routine and result in substantial losses of lives and equipment. The constant threat of RPG attack is a significant tactical advantage for insurgent forces. Other missile types, such as the Soviet SA series, and shoulder-fired Stinger are serious threats worldwide. Emerging threats such as the so-called “lob bomb” are similar in nature to the RPG and add a new dimension to this problem.
While attacks on vehicles on the ground are most prevalent, aircraft are also frequently targeted. The RAND corporation has published a report entitled “Protecting Commercial Aviation Against the Shoulder-Fired Missile Threat” (J. Chow, et al.), which is incorporated herein by reference, provides a comprehensive survey of existing and future missile threats as well as the existing countermeasures. The report concludes that there is a pressing need for a practical, reliable defense system for use against these threats. The threat is greatest for military aircraft. RPG and other shoulder-fired missile attacks on military aircraft are common, and include attacks on both fixed-wing and VTOL hovering aircraft.
Detecting Threats
Much work has been done on vehicle-mounted systems for the detection and localization of ballistic threats after they have been fired and are traveling toward their prospective target vehicle or aircraft. In general these systems rely on infra-red detectors and/or microwave radar to detect the firing of an RPG or a bullet. The systems generally provide the host vehicle with data on the type of threat and the direction that it was fired from. U.S. Pat. No. 6,980,151 to Mohan, “System and Method for Onboard Detection of Ballistic Threats to Aircraft,” describes a radar system and signal processing method for detection of missiles. U.S. Pat. No. 7,046,187 to Fullerton, et al, “System and Method for Active Protection of a Resource,” describes the use of an ultrawideband radar for threat detection. Commercially developed threat detection systems, such as Mustang Technologies “Crosshairs” RPG detection countermeasure system and Radiance Technologies “WeaponWatch” system, provide warning and directional data on fired threats. The major objective of these systems is to enable the target vehicle to quickly and accurately return fire in response to an attack. For example, in the case of a sniper attack, the target vehicle could fire back at the precise location that the bullet came from, hopefully preventing additional shots from being fired on the host vehicle. Return fire could be accomplished by, for example, a gun mounted in a turret that is aimed automatically by a system that utilizes the threat directional data provided by the threat warning system. Such a system allows rapid return fire in the case of an attack.
In the case of attack by RPG however, the objective of a defensive system should be to not only return fire, but to fire one or more countermeasures into the pathway of the approaching RPG thus stopping the RPG before it hits the target vehicle. The term “countermeasure” as used herein is broadly construed to reference any type of projectile that is capable of stopping, deflecting, or detonating an RPG or other ballistic missile or projectile before it hits its intended target. The term “projectile” in this case is construed to reference an object that can be propelled, fired and/or launched in any conventionally understood manner.
Therefore, in addition to rapid detection and data processing of a threat, which the above systems generally provide, the key to achieving an effective projectile defense system is a system that aims and fires countermeasures very quickly. For example, a typical RPG attack occurring from a range of about 50 meters allows less than one-half second between the time the RPG is fired until it strikes its target. From this it may be seen that extremely rapid aiming and firing of countermeasures is a key and primary inventive step for any missile defense system. Methods common in the art, such as turrets that rotate via ring gears and motors, or fast linear actuators, are incapable of aiming countermeasures in the timeframes outlined above. Moreover, vehicles and aircraft require defensive coverage throughout a full 360-degrees of azimuth as well as some degree of elevation. Size, weight, systemic, and cost constraints will optimally require this coverage from a single launcher system. Finally, RPG or other types of missile attacks may occur simultaneously, from different directions and/or different elevations. Existing turret-type defensive launcher systems, no matter how fast acting, can not aim at two different targets simultaneously. U.S. Pat. No. 7,190,304 to Carlson, “System for Interception and Defeat of Rocket Propelled Grenades and Method of Use,” describes a combined IR and radar RPG detection system for tactical vehicles and a means for deploying one or more countermeasures, but fails to address the above aiming requirements. Carlson discloses methods of minor course corrections for the countermeasures, but it is not likely that these methods will compensate for large aiming discrepancies. Moreover, steerable countermeasures are much more expensive and complex than countermeasures that are essentially of the point-and-shoot type. Lastly, countermeasures, relying on maneuvering will exclude some types of simple countermeasures that have been demonstrated to be effective against RPGs, such as pellet-type defensive countermeasures. U.S. Pat. No. 7,202,809 to Schade, et al., “Fast Acting Active Protection System” discloses a multi-barrel recoilless gun as the means for aiming and launching countermeasures. Schade, however does not teach how such a gun system is able to physically aim countermeasures in the extremely short timeframe described above. Moreover the system in Schade cannot engage multiple threats simultaneously or nearly simultaneously.
Several complete RPG defense systems have been proposed or are in development. Sometimes referred to as Active Protection Systems (APS), these systems generally use either an explosive kill missile or a 360-degree hail of shot pellets to defeat RPGs. While these systems can be effective, there is serious concern for collateral damage with the use of such systems. Ideally, a defensive system that deploys non-explosive countermeasures to defeat RPG's will greatly reduce the potential for unintended harm to innocent bystanders as well as friendly forces and their assets. Moreover, explosions and hails of pellets are inconsistent with the needs of an RPG defense system that is intended for aircraft deployment. An aircraft-suitable system needs to utilize a carefully-directed countermeasure to avoid damage to itself and other aircraft or dismounted troops in the vicinity. Other deficiencies in existing systems include the inability to engage multiple targets simultaneously and/or in rapid succession, and in some cases the need to reload and service the system after only a single attack. While the technology for detecting RPG attacks appears to be a reality, methods for safely and effectively delivering defensive countermeasures are largely unknown.
There is, therefore, a need for an improved RPG countermeasure delivery system for use in conjunction with available and future detection and warning systems. The system should be capable of delivering non-fratricidal RPG countermeasures, or delivering other countermeasure types in a precisely aimed manner. The system should be adaptable to ground vehicles as well as aircraft, and should be capable of engaging multiple threats simultaneously from different directions and elevations.